Engine cooling system with optionally communicable head cooling circuit and block cooling circuit, and method of operating the same

ABSTRACT

An internal combustion engine includes a cylinder head formed with a cooling jacket which has an inlet and an outlet, a cylinder block formed with a cooling jacket which has an inlet and an outlet, and a radiator. A cooling system includes: a first pump for the head jacket, a second pump for the block jacket, a temperature sensor for sensing the temperature of the cooling fluid passing in through the block inlet, a block recirculation conduit system leading from the block outlet so as to supply cooling fluid flow to the block inlet, a main recirculation conduit system of which an upstream part is communicated to the head outlet and a downstream part is communicated to the radiator inlet, a radiator output conduit system which leads from the radiator outlet both to the head inlet and also to the block inlet and which communicates the downstream part of the block recirculation conduit system to the head inlet, a first valve for controlling flow of cooling fluid through the radiator, a flow mixing conduit which communicates a part of the main recirculation conduit system with a part of the block recirculation conduit system, a second valve for controlling flow of cooling fluid through the flow mixing conduit, and a controller which receives the signal from the sensor and which controls the first and second valves.

CROSS-REFERENCE TO THE RELATED APPLICATION

The present application is a continuation-in-part application ofapplication Ser. No. 264,866 filed on May 18, 1981 now U.S. Pat. No.4,369,738.

BACKGROUND OF THE INVENTION

The present invention relates to an internal combustion engine coolingsystem, and, more particularly, relates to an internal combustion enginecooling system which provides either combined cooling for a cylinderhead and a cylinder block of the engine, or either partly or totallyseparated cooling for the cylinder head and the cylinder block,according to operational conditions.

There are various considerations which arise with regard to the coolingof internal combustion engines which are cooled by the circulation ofcooling fluid in passages or cooling jackets formed in the cylinder headand in the cylinder block thereof. Some of these considerations relateto the cooling of the cylinder head, and others to the cooling of thecylinder block. Nowadays the prior art type old or conventional ways ofcooling an internal combustion engine, in which the cooling fluid forthe cylinder head was always completely mixed with that for the cylinderblock, thus ensuring that the cylinder head and the cylinder block werealways at substantially the same temperature, have become inadequate.

One of these considerations is that it is important to maximize thethermal efficiency of an internal combustion engine, and in order to dothis it is effective to increase the compression ratio of the engine.However, increase of the compression ratio of the engine is limited bythe occurrence of so called knocking or pinking, i.e. of detonationcaused by compression ignition, not caused by any spark from a sparkplug, of the air-fuel mixture within the combustion chambers of theengine. The occurrence of knocking is generally reduced by keeping thecylinder head as cool as possible, and accordingly when an internalcombustion engine is being operated, especially in operationalconditions in which the occurrence of knocking is a high possibility,such as high rotational speed high engine load operational conditions,it is very important to cool the cylinder head down to as low atemperature as possible, consistent with other operationalconsiderations.

On the other hand, it is not very advantageous to cool down the cylinderblock of the engine to a very low temperature, because in that case thetemperature of the lubricating oil contained within the cylinder block,which is of course strongly influenced by the temperature of thecylinder block, becomes rather low, thus increasing the viscosity ofthis lubricating oil and causing unacceptably high mechanical energylosses in the engine. Further, because the viscosity of the lubricatingoil within the cylinder block when this oil is cold, i.e. when it is notat proper operating temperature, is higher than when said lubricatingoil is at operating temperature, therefore of course while thislubricating oil is cold this causes substantially increased use of fuelby the internal combustion engine, which is very wasteful. Further, ifthe temperature of the walls of the cylinders of the engine, i.e. thetemperature of the bores thereof, becomes low, then the amount ofuncombusted hydrocarbons in the exhaust gases emitted by the enginerises, which can cause a serious problem in view of the standards forcontrol of pollution by automobiles, which are becoming more and moresevere nowadays.

Another problem that occurs if the temperature of the cylinder blockgets low is that wear on the various moving parts of the internalcombustion engine, especially bore wear, rises dramatically. In fact, alarge proportion of the wear on the bores of an internal combustionengine occurs when the engine is in the non fully warmed up condition,both because the lubricating qualities of the lubricating oil in theengine are not good at low temperatures, and also because the state ofmechanical fit to which the parts of the engine are "worn in" or "runin" is appropriate to their physical dimensions when at proper engineoperating temperature, and accordingly in the cold or the semi coldcondition these parts do not mate together very well.

These problems that arise when the cylinder block of an internalcombustion engine becomes too cold during actual running operation ofthe engine of course also apply with equal force during the warming upprocess of the internal combustion engine, after it has been started upfrom the cold condition and before it has attained normal operatingtemperature. Especially, the problem of excessive wear on the movingparts of the internal combustion engine, and the problem of excessiveemission of uncombusted hydrocarbons in the exhaust gases of theinternal combustion engine, are particularly serious during warming upoperation. In fact, in view of this matter, it has in the past been animportant design goal for internal combustion engines for the movingparts thereof to be warmed up as soon as practicable, or at any rate tobe brought to an intermediate temperature higher than a very cold nonoperating temperature as soon as practicable.

According to these considerations, it is important to warm up thecylinder block of an internal combustion engine as quickly as possible,when the engine is started from the cold condition, and to keep thecylinder block at quite a high operating temperature thereafter. Adifficulty arises in this regard, because during the operation of aninternal combustion engine most of the heat which is being generated inthe combustion chambers thereof by combustion of air-fuel mixturetherein is in fact communicated not to the cylinder block of the engine,but to the cylinder head thereof. Therefore transfer of heat from thecylinder head wherein said heat is generated to the cylinder block isvery important, especially during the warming up process of the engine.Of course, such heat transfer can take place by the process of heatconduction, since the cylinder head is clamped to the cylinder block,typically however with the interposition between of a head gasket whichmay have a rather low heat conductivity. However, it is desirable toconvey heat from the cylinder head to the cylinder block, during enginewarmup, more quickly than can be accomplished by this conductionprocess, and the conventional above described mixing of the coolingfluid circulating within the cylinder head with the cooling fluidcirculating within the cylinder block, during engine warmup, iseffective for achieving this.

In the prior art, it has been proposed to provide completely independentsystems for cooling the cylinder head and for cooling the cylinderblock, in order to fulfil the first above described objective of coolingthe cylinder head to a low temperature in order to avoid knocking, whilekeeping the cylinder block warmer, and each of these systems has beenequipped with its own fluid pump, conduits, radiator, etc. However, sucha system does not provide for the above described transfer of heatduring the engine warming up process from the cylinder head to thecylinder block via the cooling fluid, and, since the cylinder block hasa considerably large heat capacity, this means that the cylinder blockdoes not warm up quickly from the cold condition, with the ill effectsdetailed above. Also, the provision of two independent cooling systemsincreases weight to an unacceptably high extent, and increasesmanufacturing cost. Further, since in the above described system twoindependent radiators are used, and the flow amount through each of themis individually regulated, it is very difficult to use total radiatorcooling capacity fully, because although in some particular set ofoperational conditions the full cooling capacity of one radiator of onecooling system may not be completely required, it is not practicable toutilize this spare cooling capacity in order to provide additionalcooling in the other cooling system, and accordingly one cooling systemmay become overloaded, while the other is not fully loaded. Thisoperational inflexibility is very troublesome.

SUMMARY OF THE INVENTION

Accordingly, it is the primary object of the present invention toprovide a cooling system, and a method for operating said coolingsystem, which improve upon the anti knock characteristic of an internalcombustion engine.

It is a further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating saidcooling system, which keep the cylinder head cool, so as to reduce thepossibility of the occurrence of knocking in the combustion chambers ofthe internal combustion engine.

It is a further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating saidcooling system, which, when the internal combustion engine has reached asteady temperature operational condition, keep the cylinder head thereofcooler than the cylinder block.

It is a further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating saidcooling system, which warm up the cylinder block of the internalcombustion engine as quickly as possible from the cold condition.

It is a further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating saidcooling system, which keep the cylinder block of the internal combustionengine considerably warm during operation thereof, thus keeping emissionof unburnt hydrocarbons in the exhaust gases of the internal combustionengine low.

It is a further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating saidcooling system, which warm up the lubricating oil in the cylinder blockof the engine quickly from the engine cold condition, and whichthereafter keep this lubricating oil hot.

It is a further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating saidcooling system, which, by warming up the cylinder block of the internalcombustion engine quickly from the cold condition, and by keeping itwarm during operation of the internal combustion engine, minimizefrictional energy losses in the engine.

It is a yet further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating saidcooling system, which minimize engine warming up time.

It is a yet further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating saidcooling system, which minimize engine wear during the engine warmupprocess of the internal combustion engine.

It is a yet further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating saidcooling system, which minimize fuel utilization during the engine warmupprocess of the internal combustion engine.

It is a yet further object of the present invention to provide a coolingsystem for an internal combustion engine which is of low weight.

It is a yet further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating thecooling system, which allow for maximum radiator cooling capacityutilization during operation of the internal combustion engine.

It is a yet further object of the present invention to provide a coolingsystem for an internal combustion engine, and a method of operating thecooling system, which provide a monitoring capacity for the lubricatingoil within the cylinder block of the internal combustion engine, and asystem for lowering the temperature thereof, should said temperaturebecome excessive.

According to the present invention, these and other objects areaccomplished by, for an internal combustion engine comprising: (a) acylinder head formed with a head cooling jacket for cooling saidcylinder head, said head cooling jacket being formed with a cylinderhead inlet and a cylinder head outlet; (b) a cylinder block formed witha block cooling jacket for cooling said cylinder block, said blockcooling jacket being formed with a cylinder block inlet and a cylinderblock outlet; and (c) a radiator formed with an inlet and an outlet; acooling system, comprising: (d) a first pump for impelling cooling fluidthrough said head cooling jacket from said cylinder head inlet towardssaid cylinder head outlet; (e) a second pump for impelling cooling fluidthrough said block cooling jacket from said cylinder block inlet towardssaid cylinder block outlet; (f) a block input fluid temperature sensorfor sensing the temperature of the cooling fluid which passes in throughsaid cylinder block inlet to said block cooling jacket, and forgenerating a sensed block input temperature signal representative ofsaid temperature; (g) a block recirculation conduit system leading fromsaid cylinder block outlet of said block cooling jacket so as to supplyflow of cooling fluid, from a downstream part of said blockrecirculation conduit system, to said cylinder block inlet of said blockcooling jacket; (h) a main recirculation conduit system, an upstreampart of which is communicated to said cylinder head outlet of said headcooling jacket, and a downstream part of which is communicated to saidinlet of said radiator; (i) a radiator output conduit system, leadingfrom said outlet of said radiator both to said cylinder head inlet ofsaid head cooling jacket and also to said cylinder block inlet of saidblock cooling jacket, said downstream part of said block recirculationconduit system being thereby communicated also to said cylinder headinlet of said head cooling jacket; (j) a first control valve forcontrolling flow of cooling fluid through said radiator according to aradiator flow regulation signal; (k) a flow mixing conduit whichcommunicates a part of said main recirculation conduit system with apart of said block recirculation conduit system; (l) a second controlvalve for controlling flow of cooling fluid through said flow mixingconduit according to a block flow regulation signal; and (m) acontroller, which receives said sensed block input temperature signalfrom said block input fluid temperature sensor, and which produces,based thereon, said radiator flow regulation signal which is sent tosaid first control valve, and also said block flow regulation signalwhich is sent to said second control valve.

According to such a structure, the controller can vary the amount ofcooling operation provided for the internal combustion engine, byvarying the opening amount of the first control valve, thus varying theamount of cooling fluid passing through the radiator, and can also varythe amount of mixing between the cooling circuit for the cylinder headand the cooling circuit for the cylinder block, by varying the openingamount of the second control valve, thus varying the amount of coolingfluid passing through the flow mixing conduit.

Further, according to a particular aspect of the present invention,these and other objects are more particularly and concretelyaccomplished by a method for operating the cooling system describedabove, when said cooling system is filled with cooling fluid, comprisingthe processes, simultaneously performed, of: (o) operating said firstpump and said second pump; and (p) depending upon said sensed blockinput temperature signal from said block input fluid temperature sensor,performing either one or the other but not both of the following twoprocesses (q) and (r): (q) if said sensed block input temperature signalfrom said block input fluid temperature sensor indicates a cooling fluidtemperature at said cylinder block inlet of said block cooling jacket ofless than a certain first predetermined temperature value, thensimultaneously: (q1) controlling said first control valve, by saidradiator flow regulation signal from said controller, so assubstantially to interrupt flow of cooling fluid through said radiator;and (q2) controlling said second control valve, by said block flowregulation signal, so as to allow a flow of cooling fluid through saidflow mixing conduit; (r) if said sensed block input temperature signalfrom said block input fluid temperature sensor indicates a cooling fluidtemperature at said cylinder block inlet of said block cooling jacket ofgreater than said first predetermined temperature value, thensimultaneously: (r1) controlling said first control valve, by saidradiator flow regulation signal from said controller, so as to allowcooling fluid to flow through said radiator; and (r2) controlling saidsecond control valve, by said block flow regulation signal, so as toallow a controlled flow of cooling fluid through said flow mixingconduit.

According to such a method, during the warming up process of theinternal combustion engine, before the cooling fluid which passes inthrough the cylinder block inlet to the block cooling jacket hasattained the first predetermined temperature, the cooling systems forthe cylinder head and for the cylinder block are substantiallycommunicated, and no substantial cooling is provided for either by theradiator, so that the heat which is supplied to the cooling fluid withinthe head cooling jacket is communicated to the cooling fluid within theblock cooling jacket, and both the cylinder head and the cylinder blockare quickly warmed up together; but, after the cooling fluid whichpasses in through the cylinder block inlet to the block cooling jackethas attained the first predetermined temperature, then according toprocess (r1) substantial cooling is provided for the cooling fluid inthe head cooling jacket, while according to process (r2) the amount ofcooling provided for the cooling fluid in the block cooling jacket isregulated. Thus, after the internal combustion engine has been warmedup, the cylinder block may be kept substantially warmer than thecylinder head.

Further, according to a particular aspect of the present invention,these and other objects are more particularly and concretelyaccomplished by a method of the sort described above, said coolingsystem further comprising an engine lubricating oil temperature sensorfor detecting the temperature of lubricating oil contained within saidcylinder block, and for producing a lubricating oil temperature signalrepresentative thereof, said lubricating oil temperature signal beingsupplied to said controller, wherein in process (r) the opening amountof said second valve is so controlled, by said block flow regulationsignal, as to allow such an amount of cooling fluid to flow through saidflow mixing conduit as to keep the sensed block input temperature signalproduced by said block input fluid temperature sensor approximately at alevel indicative of a second predetermined temperature, except that ifthe engine lubricating oil temperature signal produced by said enginelubricating oil temperature sensor is indicative of a lubricating oiltemperature of the lubricating oil contained within said cylinder blockof higher than a third predetermined temperature, then such a block flowregulation signal is supplied to said second control valve as to causesaid second control valve to open to the maximum amount; wherein saidsecond predetermined temperature is substantially higher than said firstpredetermined temperature; wherein said third predetermined temperatureis substantially higher than said second predetermined temperature; andwherein in process (r), if said temperature indicated by said sensedblock input temperature signal is substantially higher than said secondpredetermined temperature, and is less than said third predeterminedtemperature, then said second valve is so controlled, by said block flowregulation signal, as to open up said second valve wider so as todecrease its flow resistance; and, if said indicated temperature issubstantially lower than said second predetermined temperature, saidsecond valve is so controlled as to make said second valve more closedso as to increase its flow resistance.

According to such a method, by a feedback control, the cooling fluidtemperature at said cylinder block inlet of said block cooling jacket iscontrolled to be substantially equal to said second predeterminedtemperature, except in said emergency case when the temperature of saidlubricating oil contained within said cylinder block rises to higherthan said third predetermined temperature which is the dangertemperature.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be shown and described with reference toseveral preferred embodiments thereof, and with reference to theillustrative drawings. It should be clearly understood, however, thatthe description of the embodiments, and the drawings, are all of themgiven purely for the purposes of explanation and exemplification only,and are none of them intended to be limitative of the scope of thepresent invention in any way, since the scope of the present inventionis to be defined solely by the legitimate and proper scope of theappended claims. In the drawings:

FIG. 1 is a diagrammatical illustration, showing a first preferredembodiment of the cooling system according to the present invention, forpracticing a first preferred embodiment of the method according to thepresent invention, in which only the aforementioned temperature sensoris provided to the cylinder block inlet thereof; and

FIG. 2 is a diagrammatical illustration, showing a second preferredembodiment of the cooling system according to the present invention, forpracticing a second preferred embodiment of the method according to thepresent invention, in which a temperature sensor is also provided forsensing the temperature of the lubricating oil which is contained withinthe cylinder block.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to severalpreferred embodiments thereof, and with reference to the accompanyingdrawings, FIG. 1 is a diagrammatical view, showing an internalcombustion engine which is equipped with a first preferred embodiment ofthe cooling system according to the present invention, and to which afirst preferred embodiment of the method for cooling according to thepresent invention can be applied. In this figure, the reference numeral1 denotes the internal combustion engine, which comprises a cylinderhead 2 and a cylinder block 3, which are clamped together, optionallywith the intervention therebetween of a cylinder head gasket which isnot shown.

The internal combustion engine 1 includes at least one combustionchamber, which is not shown, and the cylinder head 2 defines the upperpart of this combustion chamber, i.e. the part thereof in which thecompression and the ignition occurs, and the surface of which upper parttherefore receives the greater proportion of the heat generated in saidcombustion chamber. The cylinder head 2 is formed with a head coolingjacket 4 which extends close to a large part of said upper part of saidcombustion chamber, so as, when said head cooling jacket 4 is filledwith cooling fluid such as water, to cool said upper part of saidcombustion chamber, and said cylinder head 2. Typically, the internalcombustion engine 1 will in fact include several such combustionchambers, and the head cooling jacket 4 will extend past the upper partsof each of these combustion chambers. Cooling fluid is supplied into thehead cooling jacket 4 through a cylinder head inlet 5, and is taken outfrom the head cooling jacket 4 through a cylinder head outlet 8.

Similarly, the cylinder block 3 is formed with a block cooling jacket 5which extends close to a large part of the side wall defining surface ofsaid combustion chamber, so as, when said block cooling jacket 5 isfilled with cooling fluid, to cool said side wall part of saidcombustion chamber, and said cylinder block 5. Again, of course,typically the cylinder block 5 will in fact define several suchcombustion chamber walls or bores, and the block cooling jacket 5 willextend past the side wall parts of each of these bores. Cooling fluid issupplied into the block cooling jacket 5 through a cylinder block inlet7, and is taken out from the block cooling jacket 5 through a cylinderblock outlet 9.

Further, a cooling radiator 16 of a conventional sort, formed with aninlet at its upper portion and an outlet at its lower portion, isprovided for the internal combustion engine 1.

As has been previously explained, during operation of the internalcombustion engine 1, the major portion of the heat generated in thecombustion chambers thereof is communicated to the cylinder head 2, andonly a minor portion of the heat generated in the combustion chambers iscommunicated directly to the cylinder block 3 of the internal combustionengine 1. Therefore, an imbalance of heating occurs between the cylinderhead 2 and the cylinder block 3, and a first preferred embodiment of thecooling system according to the present invention for cooling theinternal combustion engine 1, along with a first preferred embodiment ofthe method for cooling according to the present invention practiced bysaid first preferred cooling system embodiment, which correct saidimbalance, will now be explained.

A cylinder head pump 10 is provided proximate to the cylinder head inlet6, for impelling cooling fluid through the head cooling jacket 4 fromthe cylinder head inlet 6 to the cylinder head outlet 8; and, similarly,a cylinder block pump 11 is provided, proximate to the cylinder blockinlet 7, for impelling cooling fluid from the cylinder block inlet 7 tothe cylinder block outlet 9. To the cylinder head outlet 8 there isconnected the upstream end of a head output conduit 12, and to thecylinder block outlet 9 there is connected the upstream end of a blockrecirculation conduit 13. The end remote from the internal combustionengine 1 of the head output conduit 12 is communicated to the upstreamend of a main recirculation conduit 15, which is of relatively low flowresistance compared to the block recirculation conduit 13, and at anintermediate part of which there is provided a radiator flow regulationvalve 14. The downstream end of the main recirculation conduit 15 isconnected to the inlet of the radiator 16. The outlet of the radiator 16is connected to the upstream end of a radiator output conduit 17, whosedownstream end is connected to the upstream end of a head input conduit18 and also to the upstream end of a block input conduit 19. Thedownstream end of the head input conduit 18 is directly connected to theinput of the cylinder head pump 10, and the downstream end of the blockinput conduit 19 is connected to the input of the cylinder block pump11.

To an intermediate point of the block recirculation conduit 13 there isconnected the upstream end of a flow mixing conduit 24, at anintermediate point of which there is provided a block transfer flowregulation valve 25, which regulates the flow rate of cooling fluidthrough said flow mixing conduit 24; and the downstream end of the flowmixing conduit 24 is connected to an intermediate point of the mainrecirculation conduit 15, upstream of the radiator flow regulation valve14. Finally, the downstream end of the block recirculation conduit 13,which is somewhat restricted and has a relatively high resistance toflow of cooling fluid, is connected to an intermediate part of the blockinput conduit 19, and accordingly the block recirculation conduit 13communicates the cylinder block outlet 9 directly to the inlet of thecylinder block pump 11, bypassing the radiator 16.

A heater 22 is fed, via an input conduit 21 and an output conduit 23,with part of the cooling fluid flow which is available in the blockrecirculation conduit 13, via a heater flow control valve 20, in aselective manner.

The radiator flow regulation valve 14 and the block transfer flowregulation valve 25 are controlled by means of valve control signalswhich are sent to them, which will hereinafter be explained. In theshown preferred embodiment of the cooling system according to thepresent invention, in fact, these valve control signals are electricalsignals, and the radiator flow regulation valve 14 and the blocktransfer flow regulation valve 25 may be diaphragm actuated coolingfluid valves, their diaphragms being actuated by supply of inletmanifold vacuum thereto which is controlled by electrically controlledvacuum switching valves of per se well known sorts. However, inalternative embodiments, the radiator flow regulation valve 14 and theblock transfer flow regulation valve 25 might be directly actuated bysupply of electrical energy thereto, via linear motors, solenoids, orthe like; this would be quite within the scope of the present invention.

At the cylinder block inlet 7, or in the block input conduit 19, eitherupstream or downstream of the cylinder block pump 11, but definitelydownstream of the point at which the block recirculation conduit 13joins the block input conduit 19, there is mounted a block input fluidtemperature sensor 26, which senses the temperature of the cooling fluidwhich is passing in through the cylinder block inlet 7 to the blockcooling jacket 5, and which generates a sensed temperature signalrepresentative thereof. This sensed temperature signal output from thissensor 26 is sent to a controller 27. The controller 27, based upon thesensed temperature signal received from the block input fluidtemperature sensor 26, outputs the aforesaid valve control electricalsignals for controlling the radiator flow regulation valve 14 and theblock transfer flow regulation valve 25, according to control logicwhich will be explained hereinafter with respect to the first preferredembodiment of the method according to the present invention.

This controller 27 may be a simple electrical switching systemincorporating relays, solenoids, and the like, constructed in a fashionwhich will be readily conceived of by a person of ordinary skill in theart pertaining thereto, based upon the disclosure of the function ofsaid controller 27 which is contained hereinafter; but, in fact, in theshown first preferred embodiment of the cooling system according to thepresent invention, this controller 27 is an on board computer,incorporating a microprocessor, and this computer 27 also, in a timeshared fashion, performs various other regulatory functions for theinternal combustion engine 1. However, the use of such a computerincorporating a microprocessor is not essential.

Now, the operation of the first preferred embodiment of the coolingsystem according to the present invention described above, according tothe first preferred embodiment of the method according to the presentinvention, will be explained.

Effectively, the controller 27 recognizes two distinct operationalconditions for the internal combustion engine 1, according to thetemperature of the cooling fluid which is passing into the block coolingjacket 5 through the cylinder block inlet 7, as sensed by the blockinput fluid temperature sensor 26, and as indicated by the temperaturesignal received therefrom, and provides, in these two differentoperational conditions, different forms of control for the radiator flowregulation valve 14, and for the transfer flow regulation valve 25, viathe valve and pump control signals therefor which said controller 27outputs.

First, if the sensed temperature signal from the block input fluidtemperature sensor 26 indicates a temperature of the cooling fluidpassing in through the cylinder block inlet 7 to the block coolingjacket 5, i.e. the temperature of the cooling fluid which has just beenattained by the mixing of the cooling fluid flowing out from the headcooling jacket 4 and the cooling fluid flowing out from the blockcooling jacket 5, of less than a certain predetermined temperaturevalue, which for example may be 90° C., then it is considered, accordingto this first preferred embodiment of the cooling method according tothe present invention, that the internal combustion engine 1 is beingwarmed up from the cold condition. At this time, the controller 27generates valve control signals for the radiator flow regulation valve14 and the block transfer flow regulation valve 25 which cause theradiator flow regulation valve 14 to be completely closed, and whichcause the block transfer flow regulation valve 25 to be completelyopened.

The effect of this mode of operation provided by the controller 27 isthat, since the radiator flow regulation valve 14 is kept completelyclosed by the valve control signal fed thereto, no fluid flow can occurat this time through the main recirculation conduit 15, the radiator 16,and the radiator output conduit 17. In this connection, it should beunderstood that the provision of the radiator flow regulation valve 14at an intermediate part of the radiator output conduit 17, instead of ina position as shown in FIG. 1 at an intermediate part of the mainrecirculation conduit 15, would be consistent with the principles of thepresent invention, as providing the same function. Therefore, the flowof cooling fluid from the cylinder head outlet 8 enters entirely intothe upper end in the figure of the flow mixing conduit 24, passing theblock transfer flow regulation valve 25 substantially withoutobstruction since this block transfer flow regulation valve 25 is open,and meets the flow of cooling fluid which is passing out from thecylinder block outlet 9 through the block recirculation conduit 13.These flows of cooling fluid thus flow together down along the blockrecirculation conduit 13, mixing therein with one another, and then flowinto the intermediate portion of the block input conduit 19 to which thedownstream end of the block recirculation conduit 13 is communicated.Therefrom, a part of this cooling fluid is supplied to the inlet side ofthe cylinder block pump 11, and also a part of this cooling fluid flowsthrough the block input conduit 19 in the right to left direction in thefigure to be supplied to the upstream end of the head input conduit 18via the downstream portion of the radiator output conduit 17 remote fromthe radiator 16. From the head input conduit 18, this flow then issupplied to the inlet side of the cylinder head pump 10, which pumps itback into the head cooling jacket 4 of the cylinder head 3. In thisconnection, it should be understood that the block recirculation conduit13 is somewhat restricted, and, particularly, offers a greaterresistance to flow of cooling fluid than does the main recirculationconduit 15, for reasons which will become apparent later.

Of course, at this time, substantially no cooling action at all isprovided in this mode of operation by the cooling system according tothe present invention to the internal combustion engine 1 as a whole,because the radiator 16 is receiving no flow of cooling fluid; and theoperation of the shown first preferred embodiment of the cooling systemaccording to the present invention is only to redistribute heat which isbeing produced by combustion within the combustion chambers of theinternal combustion engine 1 from the cylinder head 2 thereof, whichdirectly receives most of the generated heat, to the cylinder block 3thereof which directly receives only a minor part of the generated heat.In this connection, it will be understood that no very high speed flowof cooling fluid is necessary at this time through the head coolingjacket 4 of the cylinder head 2, or through the block cooling jacket 5of the cylinder block 3, since it is intended that the internalcombustion engine 1 as a whole should heat up, in this operationalcondition, and no overall cooling action therefor is now required.Accordingly, although the block recirculation conduit 13 is somewhatrestricted, and has a high flow resistance, the flow therethrough willbe quite sufficient. As a result of the above explained mode ofoperation, the warming up characteristic of the cylinder block 3 is muchimproved, as compared with the case in which the cooling system for thecylinder head 2 is entirely separated from the cooling system for thecylinder block 3. Since it is desirable to raise the temperature of thecylinder block 3 fairly quickly from the cold condition, in order tominimize frictional losses during the warming up process of the internalcombustion engine by heating up the lubricating oil contained within itas quickly as possible, and also in order to minimize fuel utilizationduring engine warmup, and in order to minimize engine wear, especiallycylinder bore wear, before the engine block is fairly hot, as explainedabove, as well as to minimize the emission of improperly combustedhydrocarbons in the exhaust gases of the engine when it is beingoperated in the cold condition, the above described constructionaccording to the first preferred embodiment of the cooling systemaccording to the present invention is very advantageous.

On the other hand, if the sensed temperature signal produced by theblock input fluid temperature sensor 26 indicates that the temperatureof the cooling fluid flowing into the block cooling jacket 5 of thecylinder block 3 through the cylinder block inlet 7, i.e. thetemperature of the cooling fluid which has just been attained by themixing of the cooling fluid flowing out from the head cooling jacket 4and the cooling fluid flowing out from the block cooling jacket 5, isgreater than the above mentioned predetermined temperature value, i.e.in this case 90° C., then in this second operational condition thecontroller 27 generates a different set of control signals for theradiator flow regulation valve 14, and for the block transfer flowregulation valve 25, as follows.

The valve control signal output to the radiator flow regulation valve 14at this time is such as to keep the radiator flow regulation valve 14completely open. Thus, cooling fluid is now allowed to pass through theradiator flow regulation valve 14 without encountering any substantialflow resistance, into the main recirculation conduit 15, and to theinlet of the radiator 16. Thus, cooling fluid which has passed throughthe head cooling jacket 4 and has been heated therein flows out throughthe cylinder head outlet 8, through the head output conduit 12, into theupstream end of the main recirculation conduit 15, past the radiatorflow regulation valve 14, and along through the main recirculationconduit 15 to its downstream end, whence it enters into the inlet of theradiator 16. This flow of cooling fluid is then cooled within theradiator 16 in a per se well known fashion, and passes out of the outletof the radiator 16 into the upstream end of the radiator output conduit17, along which it flows, and from the downstream end of which it passesinto the upstream end of the head input conduit 18. Then, this coolingfluid passes through the head input conduit 18 to be supplied to theinlet of the cylinder head pump 10, which pumps it into the cylinderhead inlet 6, whence it is returned to the head cooling jacket 4.

Further, at this time, the controller 27 outputs a valve control signalto the block transfer flow regulation valve 25 which controls it in thefollowing manner. When the sensed temperature signal received by thecontroller 27 from the block input fluid temperature sensor 26 indicatesa temperature of the cooling fluid flowing in through the cylinder blockinlet 7 to the block cooling jacket 5 of less than a secondpredetermined temperature value, which is higher than the abovementioned first predetermined temperature value which in this firstpreferred embodiment is 90° C., and for instance may be 95° C., then thecontroller 27 outputs a control signal to the block transfer flowregulation valve 25 which causes said valve 25 to be substantiallycompletely closed, and accordingly in this condition no cooling fluidcan flow through the flow mixing conduit 24, either from theintermediate part of the block recirculation conduit 13 connectedthereto, along said flow mixing conduit 24, into the upstream end of themain recirculation conduit 15 and down past the radiator flow regulationvalve 14, which is situated in an intermediate position within the mainrecirculation conduit 15, to flow into the inlet of the radiator 16 andfrom the outlet thereof, after being cooled, into the head coolingjacket 4, or vice versa from the downstream end of the head outputconduit 12 connected thereto, along said flow mixing conduit 24, intothe intermediate part of the block recirculation conduit 13 connectedthereto. Accordingly, by the pumping action of the cylinder block pump11, all of the flow of cooling fluid through the block cooling jacket 5is forced into the upstream end of the restricted block recirculationconduit 13, and passes down through the block recirculation conduit 13to be supplied from its downstream end back to the inlet of the cylinderblock pump 11, without being substantially cooled. Thus, in thiscondition, since all of the cooling fluid which is passing through theblock cooling jacket 5 is being recirculated to the inlet of thecylinder block pump 11 to be returned into the block cooling jacket 5without being substantially cooled, thereby the temperature of thecooling fluid within the block cooling jacket 5 and at the cylinderblock outlet 9 thereof increases, while on the other hand, since all ofthe cooling fluid which is passing through the head cooling jacket 4 isbeing passed through the radiator 16 before being recirculated to theinlet of the cylinder head pump 10 to be returned into the head coolingjacket 4, thereby the temperature of the cooling fluid within the headcooling jacket 4 decreases.

On the other hand, when the sensed temperature signal received by thecontroller 27 from the block input fluid temperature sensor 26 indicatesa temperature of the cooling fluid flowing in through the cylinder blockinlet 7 to the block cooling jacket 5 of the cylinder block 3 which isgreater than said second predetermined temperature value, i.e. in thiscase greater than 95° C., then the controller 27, based upon this sensedtemperature signal, generates a valve control signal which controls theblock transfer flow regulation valve 25 to be partially or entirelyopened, so that a substantial amount of cooling fluid, after havingpassed through the block cooling jacket 5 and having been heatedtherein, passes from an intermediate portion of the block recirculationconduit 13 into the lower end in FIG. 1 of the flow mixing conduit 24,and passes the block transfer flow regulation valve 25, to enter intothe upstream end of the main recirculation conduit 15, to pass the openradiator flow regulation valve 14 and to flow towards the radiator 16.After having been cooled in the radiator 16, this cooled cooling fluidflow enters the upstream end of the radiator output conduit 17 andpasses out from the downstream end thereof into the block input conduit19 to be sucked in by the inlet of the cylinder block pump 11, and to bedriven thereby back into the block cooling jacket 5. At this time,because the block recirculation conduit 13 is restricted, and has afairly high resistance to flow of cooling fluid, quite a large amount ofthe flow of cooling fluid which is being expelled through the cylinderblock outlet 9 into the block recirculation conduit 13 passes throughthe flow mixing conduit 24 to be cooled in the radiator 16, in fact asmuch as can pass the block transfer flow regulation valve 25, accordingto the degree of opening of the block transfer flow regulation valve 25provided by the controller 27, and only a part of this cooling fluidpasses along the block recirculation conduit 13 to be recirculateddirectly to the inlet of the cylinder block pump 11 without beingcooled. Accordingly, quite a large proportion of the flow of coolingfluid through the block cooling jacket 5 is cooled by being passedthrough the radiator 16, and accordingly the temperature of the coolingfluid within the block cooling jacket 5 drops.

By the combination of these two actions of the controller 27 to open andto close the block transfer flow regulation valve 25, according towhether the sensed temperature signal received by the controller 27 fromthe block input fluid temperature sensor 26 indicates a temperature ofthe cooling fluid flowing in through the cylinder block inlet 7 to blockcooling jacket 5 of less than said second predetermined temperaturevalue, exemplarily 95° C., or alternatively the sensed temperaturesignal received by the controller 27 from the block input fluidtemperature sensor 26 indicates a temperature of the cooling fluidflowing in through the cylinder block inlet 7 to the block coolingjacket 5 of greater than said second predetermined temperature value,therefore, in a feedback manner, the temperature of the cooling fluidpassing in through the cylinder block inlet 7 to the block coolingjacket 5 is maintained substantially to be at the second above describedpredetermined temperature value, which in the shown first embodiment is95° C. This means that the temperature of the cylinder block 3 as awhole is maintained substantially at the second predeterminedtemperature value, i.e. in the shown first preferred embodiment, at 95°C., which is of course substantially higher than the temperature atwhich the cylinder head 2 is being maintained at this time, since thecooling fluid which is circulating through the head cooling jacket 4 isentirely, as described above, cooling fluid which has passed through theradiator 16 to be cooled. Accordingly, by thus keeping the cylinder head2 substantially cooler than the cylinder block 3 during warmed upoperation of the internal combustion engine 1, the cylinder block 3 maybe kept significantly hotter than is possible with a conventionalcooling system in which the head cooling fluid and the block coolingfluid are both always being passed through the same radiator and arebeing cooled together. Further, the temperature of the lubricating oilcontained within the internal combustion engine 1 is at this time keptat at least the temperature of the cylinder block 3, and in fact ismaintained at a significantly higher temperature, due to the dissipationof mechanical energy therein. Of course, by keeping the cylinder head 2as cool as possible, and by using as much of the capacity of theradiator 16 as possible for cooling the cylinder head 2, the possibilityof the occurrence of knocking or pinking in the internal combustionengine 1 is greatly reduced. The keeping of the cylinder block 3 as hotas possible within a predetermined limit, i.e. substantially at thesecond predetermined temperature value, of exemplarily 95° C., ensuresthat frictional losses in the internal combustion engine 1 are kept aslow as possible, and also is beneficial with regard to the minimizationof the amount of improperly combusted hydrocarbons which are emitted inthe exhaust gases of the internal combustion engine. Further, incontrast to a conventional type of cooling system as discussed abovewhich uses completely separate cooling systems for the cylinder head andfor the cylinder block, the full capacity of the radiator 16 can beeffectively utilized, according to the first embodiment of the presentinvention described above, because of the flexibility available fordetermining the proportions of the cooling capacity of the radiatorwhich can be allocated to the cylinder head 2 and to the cylinder block3 for cooling them.

In FIG. 2, there is shown in a schematic view by a diagrammaticaldrawing a second preferred embodiment of the cooling system according tothe present invention, which practices another preferred embodiment ofthe method for cooling according to the present invention. In FIG. 2,parts which correspond to parts of the first preferred embodiment of thecooling system according to the present invention shown in FIG. 1, andwhich have the same functions, are designated by the same referencenumerals as in that figure.

This second preferred embodiment of the cooling system according to thepresent invention differs from the first preferred embodiment of thecooling system according to the present invention shown in FIG. 1, onlyin that a lubricating oil temperature sensor 28 which is provided to thecylinder block 3 detects the temperature of the lubricating oilcontained within the cylinder block 3, and produces a lubricating oiltemperature signal representative thereof, said lubricating oiltemperature signal being sent to the controller 27.

The method of functioning of this second preferred embodiment of thecooling system according to the present invention is similar to that ofthe first preferred embodiment of the cooling system according to thepresent invention shown in FIG. 1, except in the following way. In thefirst operational condition, when the sensed temperature signal from theblock input fluid temperature sensor 26 indicates a cooling fluidtemperature of the cooling fluid flowing in through the cylinder blockinlet 7 to the block cooling jacket 5 which is less than said firstpredetermined temperature of for example 90° C., then the operationaccording to the present invention of this second preferred embodimentof the cooling system according to the present invention is the same asthat of the first preferred embodiment of the cooling system accordingto the present invention shown in FIG. 1 and described above: theradiator flow regulation valve 14 is kept completely closed, by beingfed with an appropriate valve control signal from the controller 27; andthe block transfer flow regulation valve 25 in the flow mixing conduit24 is kept completely open, by being fed with an appropriate valvecontrol signal, also, by the controller 27. On the other hand, when thetemperature as sensed by the block input fluid temperature sensor 26 ofthe cooling fluid flowing into the block cooling jacket 5 attains theaforesaid first predetermined temperature, in this example 90° C., thenthe cooling system according to this second preferred embodiment of thecooling system according to the present invention goes into its secondmode of operation.

In this second mode of operation, the radiator flow regulation valve 14is fully opened, by appropriate valve control signals sent thereto bythe controller 27, so as to cool the cylinder head 2 as much as possiblein order to prevent knocking, and the block transfer flow regulationvalve 25 is controlled in the same feedback manner as explained withregard to the operation of the first preferred embodiment shown in FIG.1, in order to keep the temperature of the cooling fluid flowing intothe block cooling jacket 5 of the cylinder block 3 at substantially thesecond predetermined temperature, for example 95° C., except that, ifthe lubricating oil temperature signal provided to the controller 27 bythe lubricating oil temperature sensor 28 indicates a temperature of thelubricating oil within the cylinder block 3 of greater than a certainpredetermined danger temperature, for example 120° C., then thecontroller 27 outputs a valve control signal to the block transfer flowregulation valve 25 which opens said block transfe flow regulation valveto the maximum amount, so as quickly to cool the lubricating oil withinthe cylinder block 3, in an emergency fashion. In other words, theeffective preset second predetermined temperature of the cooling fluidflowing into the block cooling jacket 5 of the cylinder block 3, whichis being maintained by the aforesaid feedback regulation, is lowered.

Further, with regard to the matter of the heater 22 fitted in theautomobile passenger compartment, when this is fitted, as is shown inFIGS. 1 and 2 and is customary, so as to use heated cooling fluiddiverted, via conduits 21 and 23, from an intermediate part of the blockrecirculation conduit 13, so as to use cooling fluid from the cylinderblock 3 for heating the heater core, rather than cooling fluid from thecylinder head 2, or a mixture of cooling fluid from the cylinder block 3and the cylinder head 2, then a better heating effect is made available,because the cooling fluid of the cylinder block 3 is, as explainedabove, generally hotter than is the cooling fluid of the cylinder head2.

Thus, it is seen that, in this second preferred embodiment of thecooling system according to the present invention also, the variousadvantages and benefits of the present invention are available. Theoccurence of knocking in the cylinders of the internal combustion engine1 is guarded against by keeping the cylinder head 2 cool, and at thesame time the cylinder block 3 is kept warmer than in the type of priorart wherein the block cooling fluid flow and the head cooling fluid aremixed at all times. Further, the warming up time for the internalcombustion engine 1 is kept minimal, and hence wear thereof duringwarming up, and consumption of fuel during this warm up period, areminimized. Yet further, in this second preferred embodiment, overheatingof the lubricating oil within the cylinder block 3 is guarded against byan emergency monitoring system.

Although the present invention has been shown and described withreference to several preferred embodiments thereof, and in terms of theillustrative drawings, it should not be considered as limited thereby.Various possible modifications, omissions, and alterations could beconceived of by one skilled in the art to the form and the content ofany particular embodiment, without departing from the scope of thepresent invention. Therefore it is desired that the scope of the presentinvention, and of the protection sought to be granted by Letters Patent,should be defined not by any of the perhaps purely fortuitous details ofthe shown embodiments, or of the drawings, but solely by the scope ofthe appended claims, which follow.

What is claimed is:
 1. For an internal combustion engine comprising:(a)a cylinder head formed with a head cooling jacket for cooling saidcylinder head, said head cooling jacket being formed with a cylinderhead inlet and a cylinder head outlet; (b) a cylinder block formed witha block cooling jacket for cooling said cylinder block, said blockcooling jacket being formed with a cylinder block inlet and a cylinderblock outlet; and (c) a radiator formed with an inlet and an outlet; acooling system, comprising: (d) a first pump for impelling cooling fluidthrough said head cooling jacket from said cylinder head inlet towardssaid cylinder head outlet; (e) a second pump for impelling cooling fluidthrough said block cooling jacket from said cylinder block inlet towardssaid cylinder block outlet; (f) a block input fluid temperature sensorfor sensing the temperature of the cooling fluid which passes outthrough said cylinder block inlet to said block cooling jacket, and forgenerating a sensed block input temperature signal representative ofsaid temperature; (g) a block recirculation conduit system leading fromsaid cylinder block outlet of said block cooling jacket so as to supplyflow of cooling fluid, from a downstream part of said blockrecirculation conduit system, to said cylinder block inlet of said blockcooling jacket; (h) a main recirculation conduit system, an upstreampart of which is communicated to said cylinder head outlet of said headcooling jacket, and a downstream part of which is communicated to saidinlet of said radiator; (i) a radiator output conduit system, leadingfrom said outlet of said radiator both to said cylinder head inlet ofsaid head cooling jacket and also to said cylinder block inlet of saidblock cooling jacket, said downstream part of said block recirculationconduit system being thereby communicated also to said cylinder headinlet of said head cooling jacket; (j) a first control valve forcontrolling flow of cooling fluid through said radiator according to aradiator flow regulation signal; (k) a flow mixing conduit whichcommunicates a part of said main recirculation conduit system with apart of said block recirculation conduit system; (l) a second controlvalve for controlling flow of cooling fluid through said flow mixingconduit according to a block flow regulation signal; and (m) acontroller, which receives said sensed block input temperature signalfrom said block input fluid temperature sensor, and which produces,based thereon, said radiator flow regulation signal which is sent tosaid first control valve, and also said block flow regulation signalwhich is sent to said second control valve; (n) whereby said controllercan vary the amount of cooling operation provided for said internalcombustion engine, by varying the opening amount of said first controlvalve, thus varying the amount of cooling fluid passing through saidradiator; and can also vary the amount of mixing between the coolingcircuit for said cylinder head and the cooling circuit for said cylinderblock, by varying the opening amount of said second control valve, thusvarying the amount of cooling fluid passing through said flow mixingconduit.
 2. A cooling system according to claim 1, wherein the flowresistance of said block recirculation conduit system, from said partthereof to which said flow mixing conduit is communicated, to saiddownstream part thereof, is substantially higher than the flowresistance of the series combination of (a) said main recirculationconduit system from said part thereof to which said flow mixing conduitis communicated to said inlet of said radiator; (b) said radiator; and(c) said radiator output conduit system from said outlet of saidradiator to the part of said radiator output conduit system communicatedto said cylinder block inlet of said block cooling jacket; whereby, themore said controller opens said second control valve, by supply of saidblock flow regulation signal thereto, the more of the flow of coolingfluid through said block cooling jacket will pass through said mainrecirculation conduit system to be cooled in said radiator, without anyrisk that said block jacket cooling fluid flow should passpreferentially through said block recirculation conduit system.
 3. Acooling system according to claim 1, wherein said first control valve ismounted upstream of said inlet of said radiator in an intermediate partof said main recirculation conduit system which is downstream of thepart of said main recirculation system to which said flow mixing conduitcommunicates.
 4. A cooling system according to claim 1, wherein saidfirst control valve is mounted in an intermediate part of said radiatoroutput conduit system.
 5. A cooling system according to claim 1, furthercomprising a heater which is supplied with cooling fluid which isdiverted from an intermediate part of said block recirculation conduitsystem; whereby said heater may be provided with cooling fluid which isas warm as practicable.
 6. A cooling system according to claim 1,wherein said controller, depending on said sensed block inputtemperature signal from said block output fluid temperature sensor,either(n) if said sensed block input temperature signal from said blockinput fluid temperature sensor indicates a cooling fluid temperature atsaid cylinder block inlet of said block cooling jacket of less than acertain first predetermined temperature value, then simultaneously:(n1)controls said first control valve, by said radiator flow regulationsignal, so as substantially to interrupt the flow of cooling fluidthrough said radiator; and (n2) controls said second control valve, bysaid block flow regulation signal, so as to allow a substantial flow ofcooling fluid through said flow mixing conduit; or (o) if said sensedblock input temperature signal from said block input fluid temperaturesensor indicates a cooling fluid temperature at said cylinder blockinlet of said block cooling jacket of greater than said firstpredetermined temperature value, then simultaneously:(o1) controls saidfirst control valve, by said radiator flow regulation signal, so as toallow cooling fluid to flow through said radiator; and (o2) controlssaid second control valve, by said block flow regulation signal, so asto allow a controlled flow of cooling fluid through said flow mixingconduit; (p) whereby, during the warming up process of said internalcombustion engine, before the cooling fluid which passes in through saidcylinder block inlet to said block cooling jacket has attained saidfirst predetermined temperature, the cooling systems for said cylinderhead and for said cylinder block are substantially communicated, and nosubstantial cooling is provided for either by said radiator, so that theheat which is supplied to the cooling fluid within the head coolingjacket is communicated to the cooling fluid within the block coolingjacket, and both the cylinder head and the cylinder block are quicklywarmed up together; but, after said cooling fluid which passes inthrough said cylinder block inlet to said block cooling jacket hasattained said first predetermined temperature, then according to saidcontrol performed by said controller according to action (o1)substantial cooling is provided for the cooling fluid in said headcooling jacket, while according to said control performed according toaction (o2) the amount of cooling provided for the cooling fluid in saidblock cooling jacket is regulated; whereby, after said internalcombustion engine has been warmed up, said cylinder block may be keptsubstantially warmer than said cylinder head.
 7. A cooling systemaccording to claim 6, wherein said controller, in case (o1), alwayscontrols said first control valve so as to keep said first control valvefully open; whereby, after the cooling fluid which passes in throughsaid cylinder block inlet to said block cooling jacket has attained saidfirst predetermined temperature, then said cylinder head is alwayscooled to the maximum possible amount, by the cooling action of saidradiator.
 8. A cooling system according to either claim 6 or claim 7,wherein in case (o) said controller so controls the opening amount ofsaid second valve, by said block flow regulation signal, as to allowsuch an amount of cooling fluid to flow through said flow mixing conduitas to keep the sensed block input temperature signal produced by saidblock input fluid temperature sensor approximately at a level indicativeof a second predetermined temperature; whereby the temperature of saidcylinder block is controlled to be substantially constant.
 9. A coolingsystem according to claim 8, wherein said second predeterminedtemperature is substantially higher than said first predeterminedtemperature; whereby the temperature of said cylinder block iscontrolled to be substantially higher than the temperature of saidcylinder head.
 10. A cooling system according to claim 9, wherein incase (o), if said temperature indicated by said sensed block inputtemperature signal is substantially higher than said secondpredetermined temperature, then said controller controls said secondvalve, by said block flow regulation signal, so as to open up saidsecond valve wider so as to decrease its flow resistance; and, if saidindicated temperature is substantially lower than said secondpredetermined temperature, said controller controls said second valve soas to make said second valve more closed so as to increase its flowresistance; whereby, by a feedback control, the cooling fluidtemperature at said cylinder block inlet of said block cooling jacket iscontrolled to be substantially equal to said second predeterminedtemperature.
 11. A cooling system according to any one of claims 1-5,further comprising an engine lubricating oil temperature sensor fordetecting the temperature of lubricating oil contained within saidcylinder block, and for producing a lubricating oil temperature signalrepresentative thereof, said lubricating oil temperature signal beingsupplied to said controller.
 12. A cooling system according to eitherone of claims 6 and 7, further comprising an engine lubricating oiltemperature sensor for detecting the temperature of lubricating oilcontained within said cylinder block, and for producing a lubricatingoil temperature signal representative thereof, said lubricating oiltemperature signal being supplied to said controller.
 13. A coolingsystem according to claim 12, wherein in case (o) said controller socontrols the opening amount of said second valve, by said block flowregulation signal, as to allow such an amount of cooling fluid to flowthrough said flow mixing conduit as to keep the sensed block inputtemperature signal produced by said block input fluid temperature sensorapproximately at a level indicative of a second predeterminedtemperature, except that if the engine lubricating oil temperaturesignal produced by said engine lubricating oil temperature sensor isindicative of a lubricating oil temperature of the lubricating oilcontained within said cylinder block of higher than a thirdpredetermined temperature, then said controller supplies such a blockflow regulation signal to said second control valve as to cause saidsecond control valve to open to the maximum amount; whereby thetemperature of said cylinder block is controlled to be substantiallyconstant, except that if the temperature of said lubricating oilcontained within said cylinder block rises to higher than said thirdpredetermined temperature, which is the danger temperature, thenemergency cooling action is provided for said cylinder block, in orderto immediately cool down said lubricating oil contained therein.
 14. Acooling system according to claim 13, wherein said second predeterminedtemperature is substantially higher than said first predeterminedtemperature.
 15. A cooling system according to claim 14, wherein saidthird predetermined temperature is substantially higher than said secondpredetermined temperature.
 16. A cooling system according to claim 15,wherein in case (o), if said temperature indicated by said sensed blockinput temperature signal is substantially higher than said secondpredetermined temperature, and is less than said third predeterminedtemperature, then said controller controls said second valve, by saidblock flow regulation signal, so as to open up said second valve widerso as to decrease its flow resistance; and, if said indicatedtemperature is substantially lower than said second predeterminedtemperature, said controller controls said second valve so as to makesaid second valve more closed so as to increase its flow resistance;whereby, by a feedback control, the cooling fluid temperature at saidcylinder block inlet of said block cooling jacket is controlled to besubstantially equal to said second predetermined temperature, except insaid emergency case when the temperature of said lubricating oilcontained within said cylinder block rises to higher than said thirdpredetermined temperature which is the danger temperature.
 17. A methodfor operating a cooling system of an internal combustion enginehaving:(a) a cylinder head formed with a head cooling jacket for coolingsaid cylinder head, said head cooling jacket being formed with acylinder head inlet and a cylinder head outlet; (b) a cylinder blockformed with a block cooling jacket for cooling said cylinder block, saidblock cooling jacket being formed with a cylinder block inlet and acylinder block outlet; and (c) a radiator formed with an inlet and anoutlet; said cooling system, comprising: (d) a first pump for impellingcooling fluid through said head cooling jacket from said cylinder headinlet towards said cylinder head outlet; (e) a second pump for impellingcooling fluid through said block cooling jacket from said cylinder blockinlet towards said cylinder block outlet; (f) a block input fluidtemperature sensor for sensing the temperature of the cooling fluidwhich passes out through said cylinder block inlet to said block coolingjacket, and for generating a sensed block input temperature signalrepresentative of said temperature; (g) a block recirculation conduitsystem leading from said cylinder block outlet of said block coolingjacket so as to supply flow of cooling fluid, from a downstream part ofsaid block recirculation conduit system, to said cylinder block inlet ofsaid block cooling jacket; (h) a main recirculation conduit system, anupstream part of which is communicated to said cylinder head outlet ofsaid head cooling jacket, and a downstream part of which is communicatedto said inlet of said radiator; (i) a radiator output conduit system,leading from said outlet of said radiator both to said cylinder headinlet of said head cooling jacket and also to said cylinder block inletof said block cooling jacket, said downstream part of said blockrecirculation conduit system being thereby communicated also to saidcylinder head inlet of said head cooling jacket; (j) a first controlvalve for controlling flow of cooling fluid through said radiatoraccording to a radiator flow regulation signal; (k) a flow mixingconduit which communicates a part of said main recirculation conduitsystem with a part of said block recirculation conduit system; (l) asecond control valve for controlling flow of cooling fluid through saidflow mixing conduit according to a block flow regulation signal; and (m)a controller, which receives said sensed block input temperature signalfrom said block input fluid temperature sensor, and which produces,based thereon, said radiator flow regulation signal which is sent tosaid first control valve, and also said block flow regulation signalwhich is sent to said second control valve; (n) whereby said controllercan vary the amount of cooling operation provided for said internalcombustion engine, by varying the opening amount of said first controlvalve, thus varying the amount of cooling fluid passing through saidradiator; and can also vary the amount of mixing between the coolingcircuit for said cylinder head and the cooling circuit for said cylinderblock, by varying the opening amount of said second control valve, thusvarying the amount of cooling fluid passing through said flow mixingconduit; said cooling system being filled with cooling fluid; saidmethod comprising the processes, simultaneously performed, of: (o)operating said first pump and said second pump; and (p) depending uponsaid sensed block output temperature signal from said block output fluidtemperature sensor, performing either one or the other but not both ofthe following two processes (q) and (r):(q) if said sensed block outputtemperature signal from said block output fluid temperature sensorindicates a cooling fluid temperature at said cylinder block outlet ofsaid block cooling jacket of less than a certain first predeterminedtemperature value, then simultaneously:(q1) controlling said firstcontrol valve, by said radiator flow regulation signal from saidcontroller, so as substantially to interrupt flow of cooling fluidthrough said radiator; and (q2) controlling said second control valve,by said block flow regulation signal, so as to allow a flow of coolingfluid through said flow mixing conduit; (r) if said sensed block outputtemperature signal from said block output fluid temperature sensorindicates a cooling fluid temperature at said cylinder block outlet ofsaid block cooling jacket of greater than said first predeterminedtemperature value, then simultaneously:(r1) controlling said firstcontrol valve, by said radiator flow regulation signal from saidcontroller, so as to allow cooling fluid to flow through said radiator;and (r2) controlling said second control valve, by said block flowregulation signal, so as to allow a controlled flow of cooling fluidthrough said flow mixing conduit; (s) whereby, during the warming upprocess of said internal combustion engine, before the cooling fluidwhich passes out through said cylinder block outlet of said blockcooling jacket has attained said first predetermined temperature, thecooling systems for said cylinder head and for said cylinder block aresubstantially communicated, and no substantial cooling is provided foreither by said radiator, so that the heat which is supplied to thecooling fluid within the head cooling jacket is communicated to thecooling fluid within the block cooling jacket, and both the cylinderhead and the cylinder block are quickly warmed up together; but, aftersaid cooling fluid which passes out through said cylinder block outletof said block cooling jacket has attained said first predeterminedtemperature, then according to process (r1) substantial cooling isprovided for the cooling fluid in said head cooling jacket, whileaccording to process (r2) the amount of cooling provided for the coolingfluid in said block cooling jacket is regulated; whereby, after saidinternal combustion engine has been warmed up, said cylinder block maybe kept substantially warmer than said cylinder head.
 18. A methodaccording to claim 17, wherein during process (r1) said first controlvalve is so controlled as to keep said first control valve fully open;whereby, after the cooling fluid which passes out through said cylinderblock outlet of said block cooling jacket has attained said firstpredetermined temperature, then said cylinder head is always cooled tothe maximum possible amount, by the cooling action of said radiator. 19.A method according to either claim 17 or claim 18, wherein in process(r2) the opening amount of said second valve is so controlled, by saidblock flow regulation signal, as to allow such an amount of coolingfluid to flow through said flow mixing conduit as to keep the sensedblock input temperature signal produced by said block input fluidtemperature sensor approximately at a level indicative of a secondpredetermined temperature; whereby the temperature of said cylinderblock is controlled to be substantially constant.
 20. A method accordingto claim 19, wherein said second predetermined temperature issubstantially higher than said first predetermined temperature; wherebythe temperature of said cylinder block is controlled to be substantiallyhigher than the temperature of said cylinder head.
 21. A methodaccording to claim 20, wherein in process (r), if said temperatureindicated by said sensed block input temperature signal is substantiallyhigher than said second predetermined temperature, then said secondvalve is controlled, by said block flow regulation signal, so as to openup said second valve wider so as to decrease its flow resistance; and,if said indicated temperature is substantially lower than said secondpredetermined temperature, said second valve is controlled so as to makesaid second valve more closed so as to increase its flow resistance;whereby, by a feedback control, the cooling fluid temperature at saidcylinder block inlet of said block cooling jacket is controlled to besubstantially equal to said second predetermined temperature.
 22. Amethod according to either one of claims 17 and 18, said cooling systemfurther comprising an engine lubricating oil temperature sensor fordetecting the temperature of lubricating oil contained within saidcylinder block, and for producing a lubricating oil temperature signalrepresentative thereof, said lubricating oil temperature signal beingsupplied to said controller.
 23. A method according to claim 22, whereinin process (r) the opening amount of said second valve is so controlled,by said block flow regulation signal, as to allow such an amount ofcooling fluid to flow through said flow mixing conduit as to keep thesensed block input temperature signal produced by said block input fluidtemperature sensor approximately at a level indicative of a secondpredetermined temperature, except that if the engine lubricating oiltemperature signal produced by said engine lubricating oil temperaturesensor is indicative of a lubricating oil temperature of the lubricatingoil contained within said cylinder block of higher than a thirdpredetermined temperature, then such a block flow regulation signal issupplied to said second valve as to cause said second control valve toopen to the maximum amount; whereby the temperature of said cylinderblock is controlled to be substantially constant, except that if thetemperature of said lubricating oil contained within said cylinder blockrises to higher than said third predetermined temperature, which is thedanger temperature, then emergency cooling action is provided for saidcylinder block, in order to immediately cool down said lubricating oilcontained therein.
 24. A method according to claim 23, wherein saidsecond predetermined temperature is substantially higher than said firstpredetermined temperature.
 25. A method according to claim 24, whereinsaid third predetermined temperature is substantially higher than saidsecond predetermined temperature.
 26. A method according to claim 25,wherein in process (r), if said temperature indicated by said sensedblock input temperature signal is substantially higher than said secondpredetermined temperature, and is less than said third predeterminedtemperature, then said second valve is so controlled, by said block flowregulation signal, as to open up said second valve wider so as todecrease it flow resistance; and, if said indicated temperature issubstantially lower than said second predetermined temperature, saidsecond valve is so controlled as to make said second valve more closedso as to increase its flow resistance; whereby, a feedback control, thecooling fluid temperature at said cylinder block inlet input of saidblock cooling jacket is controlled to be substantially equal to saidsecond predetermined temperature, except in said emergency case when thetemperature of said lubricating oil contained within said cylinder blockrises to higher than said third predetermined temperature which is thedanger temperature.